Structure of abdomen exerciser

Claim 1

An abdomen exerciser comprising: a front frame and a rear frame joined by an intermediate frame, a seat cushion mounted on said intermediate frame at the top, two curved supports bilaterally welded to a transverse bar on said intermediate frame, two three-end links respectively pivoted to said curved supports to hold a back cushion in a first position longitudinally disposed in line with said seat cushion or a second position perpendicularly disposed above said seat cushion, and two sets of weights symmetrically mounted on said three-end links to automatically turned said back cushion to said second position, wherein: said intermediate frame has hollow front end, which receives a rear extension rod on said front frame, and a rear end terminated to a semi-circular mounting block pivotally fastened to two parallel lugs on said rear frame by a pin and a clamping retainer; each three-end link comprises a first terminal fitted over the transverse bar on said intermediate frame and either curved support to hold said back cushion, a bushing on one end of said first terminal pivotally connected to a bushing on either curved support by a pin and a set of washers and a clamping retainer and disposed at an elevation above said seat cushion, a handlebar on an opposite end of said first terminal, a second terminal having one end connected to the bushing on said first terminal and an opposite end terminated to a projecting rod to hold either set of weights by a respective spring clamp, and a third terminal having a through hole, to which either leg press is pivotally connected, a pin hole, and a side projection with a pin hole; each leg press is respectively made in the shape of an angle bar, having a free end coupled with a soft covering disposed in horizontal, a fixed end pivotally connected to the through hole on the third terminal of either three-end link by a pin and a clamping retainer, and a spring-controlled lock bolt alternatively locked in the pin hole on the third terminal of either three-end link or the pin hole on the side projection for permitting the soft covering of the respective leg press to be disposed in horizontal above said seat cushion or turned sideways.